The invention concerns a method and a device for measuring a path covered.
A corresponding path measuring a path covered by a moving object deflectable along a direction is known from practice. A first component of the path measuring device is associated with the moving object and moves with the latter. A second component of the path measuring device is stationary. The two components are coupled with one another in order to convert the motion and/or deflection of the moving object into an electric signal. This electric signal is transmitted to an evaluating device of the path measuring device and converted there into motion and/or position information.
An example of such a previously known path measuring device is a potentiometer-like sensor. A wire wound as a coil forms the first component of this sensor and the second component is formed by a contact element capable of moving along the coil winding. Depending on the position of the contact element relative to the coil winding a corresponding resistance is produced for a current flowing through coil winding and contact element, which may be converted into position information.
A further example of a known path measuring device is a magnetic or inductive path measurement. In the case of the latter a coil or a part of a condenser is connected with the moving object and a further coil or the other part of the condenser is made stationary.
Further known path measuring devices use, for example, optical sensors, the motion of a first component moved with the moving object being determined optically and converted by the stationary sensor into a corresponding motion signal. Finally, laser devices for path measurement are known.
There are different disadvantages in the case of these previously known path measuring devices.
Optical measurements are indeed very precise, but at the same time very sensitive, and only usable in the case of good visual conditions, and at the same time they are quite expensive.
Magnetic or inductive devices are sensitive to vibrations, shocks, or the like, and as a rule also are quite expensive. Potentiometer-like sensors are quite imprecise and have only a relatively short service life because of wear phenomena.